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Active Noise Reduction


Phil_P
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I have just spent a pleasant afternoon diverting myself from this dreadful weather, by installing the active noise reduction (ANR) kit that I got from Headsets Inc. in the USA.

For those who aren't aware of these systems, what they do is measure the ambient sound in your headset earcup, shift it 180 degree out of phase, and then inject that back into the earcup through a second speaker element. This has the effect of cancelling out a huge chunk of ambient noise, particularly in the sound spectrum where the passive sound reduction of a conventional headset is at it's least effective.

when it came to the fitting, there was a minor problem insofar as the wiring provided isn't set up for a P.T.T . switch in the headset ear defender dome, nor is there any obvious way round the problem. However, I found after a bit of tinkering, that the coaxial shield on the mic. plug cable was in fact wired to the required plug tip, so I was able to utilise that as my P.T.T. conductor.

The ANR modules come as ready built inserts, comprising the normal earphone speaker, the extra cancelling speaker, and the pick-up microphone for ambient sound. Ready wired onto the back of this is the electronics to generate the 'anti-sound'. these form a slip in replacement for the original headset speaker which is completely removed.

I had opted for an extra £10 worth of cable which incorporated the power feed for the headset together with new aviation style plugs for microphone and earphone audio. This meant I had a very neat install, with no need to run an extra power cable from a 9v battery case.

Probably took me a couple of hours to splice all the required cables together, following the very comprehensive and clear instructions. Everything hooked up, continuity checked and ready for sound check and..... NO BLINKING BATTERY IN THE HOUSE!

A hurried trip to Netto, and we were all set to go. I slipped on the helmet and heaset and stepped out into our yard. We are only about thirty yards from a pretty busy road, so there is a constant rumble and swish as cars and lorries fly past in the current wet conditions. Although dulled by the conventional headset, there was still a clear level of ambient noise. I then flicked on the power switch on the supplied battery box, and after about a half second delay, just about all the background noise simply vanished, to be replaced with the lightest of white noise hisses in it's place. It was truly remarkable. I can hardly wait till tomorrow to start up my motor outside to see what effect it has on those frequencies. At the moment, it looks very promising indeed.

Total cost was about £130 delivered from the States, including £25 VAT and handling charge from the post office. Probably only a saving of about £15 over buying from the UK, but sometimes you hit lucky with the VAT thing. It sounds like a lot, until you compare that with the cost of a complete aviation ANR headset from someone like Bose or Sennheiser, which is likely to come in between £400 and £500. My hearing isn't great after a debauched youth of live concerts, so protecting what I have, while at the same time making radio communication much clearer is a real boon.

I will report back tomorrow after a live engine run.

If anyone is in my vicinity and would like to try my set up, they will be more than welcome, and if anyone decides they'd like to go down this path but lacks the knowledge to do the conversion, I will happily do it for cost plus a contribution towards my red wine consumption.

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I will report back tomorrow after a live engine run.

Absolutely bl**dy brilliant!!!!

Flick the switch and WOW!

:lol::lol::lol::lol:

As a matter of interest .. does this work with other sources of noise? for example ... kids? umm nagging wife? I can see a large market sector for this!! :lol::lol::lol:

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that got a chuckle.... (the wife and kids bit)

:-)

I have had a pair for shooting for years, the are brill!!!

I have never put them in to an existing headset though!

you may well be on to something I recon.....

SW :D

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I will report back tomorrow after a live engine run.

Absolutely bl**dy brilliant!!!!

Flick the switch and WOW!

:lol::lol::lol::lol:

Can you still hear the pitch and the volume of the engine change?

The reason I ask... A few years ago I heard the pitch and volume change, so eventually landed to check (yes I was gutted and it took a minute of argument inside my head as I'd just taken off after a day of crazy wind and failed launches).

I found the flex hose connecting the exhaust had split. If I'd hadn't heard it, the exhaust would 'kissed'!!! the prop goodbye.

Cheers

Paul

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Well it doesn't give silence, so you should be able to detect changes. The note changes as revs change are detectable but very muted. What you may find is that any distraction from wind noise is seriously reduced, possibly making it easier to diagnose or spot engine issues.

Phil

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Well it doesn't give silence, so you should be able to detect changes. The note changes as revs change are detectable but very muted. What you may find is that any distraction from wind noise is seriously reduced, possibly making it easier to diagnose or spot engine issues.

Phil

In theory, it wont affect your ability to detect engine noises or any other problem one little bit. What you get is a reduction in all sound levels, you still get the same overall effect, just at a much reduced volume.

If flying without a radio, then there is minimal benefit, you could get the same results by simply sticking in a pair of foam ear plugs in before you put your muffs on. With a radio or other stuff, it allows you to have the radio at a sane level and still hear it clearly.

What would be neat is a system that allowed you to hear the wind and the rustle of the canopy fabric without the engine noise ;)

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What would be neat is a system that allowed you to hear the wind and the rustle of the canopy fabric without the engine noise ;)

How about injecting the input from a small directional shotgun mic. that you have pointing up at your wing? :o)

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  • 1 month later...
  • 2 months later...

Just thought a little update on the ANR was in order, now that I'm flying;

The battery box that I have fitted, is designed to turn off the power if the headset isn't used for about 10 minutes. While airborne the other day, I thought that it had turned itself off, as it was quite noisy. So I reached into the pocket that had the battery box in it and flicked the power off to reset it and WOW, the noise level shot up massively. The active system is truly impressive, and I wouldn't like to be flying without it, now that I know how loud it is with the system turned off. With the power back on, relative peace was restored.

Happy to let anyone in my neck of the woods try it out.

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Nice post!

Thanks!

If you get a product together I can sell it :D

Sounds like you have hit the nail on the head there, ANR has been used for a while in shooting and I have used shooting ones to fly with, one of my students has a set of Bose ones (WAY to flimsey of course)

Great idea. and post.

SW :D

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  • 2 years later...
  • 4 weeks later...

Went for a flight with the noise busters.

The Good:

Low frequency noise hugely reduced. Quite a dramatic difference between on and off.

Comfortable.

Battery seems to last a long time.

The Bad:

When turning you head to the side the microphones pick up wind noise, which adds additional noise to the speakers.

Not as good high frequency noise reduction as the best (most expensive) passive muffs.

When a cell phone is close, the circuitry picks up transmission noise.

Overall

I'm keeping them. They are so much better @ low frequencies - which is what annoys my ears the most for long periods.

I may wear ear plugs as well, (I have always done this when motoring, and it works well).

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